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[carswaps]

Any codes?

[Webby the Bear]

Deffo check that vac box 

[Webby the Bear]

... As per Andy h .s comment 

Just pull smallest pipe off front vac box.no hiss equals either you've doe work and got pipes on wrong way round or box is fubard 

[Webby the Bear]

This is with car off btw 

[Mr Gav]

Cheers Webby, I'll check it out this week, not checked for codes yet but I'll do that at the same time 

[Temetsy]

IIRC the v6 has a 'flat spot'/drop on torque/power curve around 3,5k rpm I've heard that pumping up fuel pressure would cure that strange flat spot. I have no front multiram (custom intake by previous owner that really kicks sucks *ss) and still get that weird loss of power at that rpm..

[Mr Gav]

Well the vac reservoir seems fine, pulling the pipe off and there was a distinct hiss so tonight on the way back from Missy MV6`s I did a slightly untechnical test, a blast along a dual carriageway, first at full throttle and there was the flatspot between 3500-3800 rpm. Then I repeated the test at 3/4 throttle and pulled clean all the way from just below 3000rpm through to 5000rpm.
I still don`t think it`s a misfire, it just doesn`t feel like one, hard to explain but it just doesn`t feel like one.

[VXL V6]

IIRC the v6 has a 'flat spot'/drop on torque/power curve around 3,5k rpm I've heard that pumping up fuel pressure would cure that strange flat spot. I have no front multiram (custom intake by previous owner that really kicks sucks *ss) and still get that weird loss of power at that rpm..

That power loss flat spot was noticeable on the Vectra B 2.5 / 2.6's but far more smoothed out on the Omega V6's with the help of the Multi-Ram setup.

[Webby the Bear]

Ok, so youre getting stored vacuum. thats good.

blip the throttle and watch them operate.

for the rear one get someone to jam it quickly above 5k rpm. observe.

[Marks DTM Calib]

Sounds a bit like the issue Webby had with a failed non return valve in the front vacuum tank

Yep , first thing to check 


At WOT you have very little manifold vacuum so you are reliant on the vac tank storing some

[Mr Gav]

Already checked the vac reservoir and it`s holding vacuum, whether it`s holding enough is another question but AFAIK they either work or they don`t.
Next thing is to check the multi rams are working, not too keen on blipping to 5000rpm at standstill with no load though.

[Webby the Bear]

Already checked the vac reservoir and it`s holding vacuum, whether it`s holding enough is another question but AFAIK they either work or they don`t.
Next thing is to check the multi rams are working, not too keen on blipping to 5000rpm at standstill with no load though.

You wont be able to see if they're working then As long as it's up to temp. I don't see the issue.

As for is it holding ''enough'' vacuum...

If there's a vacuum leak somewhere else (e.g. brake servo hose) could the vacuum store be depleted thus affect multiram opening operation??? Question to expert...

[Andy H]

Well the vac reservoir seems fine, pulling the pipe off and there was a distinct hiss

You did this soon after switching the engine off ?

[Broomies Mate]

Already checked the vac reservoir and it`s holding vacuum, whether it`s holding enough is another question but AFAIK they either work or they don`t.
Next thing is to check the multi rams are working, not too keen on blipping to 5000rpm at standstill with no load though.

Why not?  If the engine is up to temperature, you can hold it on the limiter for a second or two.  The limiter is there as a (conservative) limit that the engine was designed to withstand.  These engines happily rev to 7.5k for brief periods of time.

[chrisgixer]

And it won't stress the engine in the same way as it would be loaded. Anything under the Rev limit is within operating range for the engine. If not there's something wrong.